[hotfix] Fix compile error in DataStreamV2SinkTransformation

Author: reswqa

flink-datastream/src/main/java/org/apache/flink/streaming/api/transformations/DataStreamV2SinkTransformation.java

@@ -69,7 +69,7 @@ public void setChainingStrategy(ChainingStrategy strategy) {
     }
 
     @Override
-    public List<Transformation<?>> getTransitivePredecessors() {
+    protected List<Transformation<?>> getTransitivePredecessorsInternal() {
         final List<Transformation<?>> result = Lists.newArrayList();
         result.add(this);
         result.addAll(input.getTransitivePredecessors());

flink-datastream/src/test/java/org/apache/flink/datastream/impl/TestingTransformation.java

@@ -32,7 +32,7 @@ public TestingTransformation(String name, TypeInformation<T> outputType, int par
     }
 
     @Override
-    public List<Transformation<?>> getTransitivePredecessors() {
+    protected List<Transformation<?>> getTransitivePredecessorsInternal() {
         return Collections.emptyList();
     }